September 14-16, 2018, Albuquerque, New Mexico
An APRS-IS Solar-Powered Telemetry System
By Karl W. Berger, W4KRL
Abstract: APRS-IS is used as a free cloud service between Wi-Fi connected solar-powered sensors and a dedicated remote color TFT display. Weather station energy consumption is reduced by placing the microcontroller in a low power state between updates. The remote display uses an APRS SSID to filter and acknowledge messages of interest.
Beyond Line-of-Sight UHF Digital Communications with the LoRa Spread Spectrum Waveform
By Dan Fay, KG5VBY
Abstract: Semtech’s LoRa transceiver products, based off Chirp Spread Spectrum (CSS) modulation, provide high receive sensitivity for low-power, Internet-of-Things (IoT) devices. While Semtech’s LoRa transceivers are designed to provide Line-of-Sight (LoS) ranges of several miles with modest radio hardware (i.e., small duck antennas, and 25-100mW Tx power levels), the high receive sensitivity (up to -138dBm or more) of a LoRa transceiver allows for leveraging common VHF+ DX techniques to achieve ranges beyond radio line-of-sight. By using higher power levels (5W/37dBm or more), high gain antennas (14.8dBi base station Yagi, 12.4dBi mobile Yagi), and horizontal polarization, it is possible to achieve Beyond Line-of-Sight (BLoS) packet radio communications using LoRa on the 70cm band. This paper will discuss digital communications using the LoRa waveform, how BLoS communication is achieved at VHF+ frequencies, the experimental setup used in this paper, and the real-world test results. To the best of the author’s knowledge, the 218km LoRa ground-based LoRa communications distance discussed in this paper is the longest ground-based (ground station-to-ground station) LoRa communication on record.
Implementing MACA and Other Useful Improvements to Amateur Packet Radio for Throughput and Capacity
By Steven Gunderson and John Bonnett, KK6JRA
Abstract: Amateur Packet Radio suffers from low throughput and “hidden terminal problem.” A protocol appliqué within AX.25 addresses these issues. It uses unnumbered frames with sequence number extension and employs KA9Q’s Multiple Access with Collision Avoidance (MACA) media access control. Throughput improved few to several-fold and network capacity increased.
Realtime Multicast for SDR Module Interconnection
By Phil Karn, KA9Q
Abstract: I have developed a set of software deVned radio receiver modules to demonstrate the utility of standard Internet real-time and multicast protocols for interprocess communication. The multicast streams convey complex digital IF sample streams, uncompressed and compressed audio and decoded physical layer frames (e.g., AX.25). One module can feed any number of others, and it is easy to move and restart individual modules without restarting the entire system. The package is currently being used for general analog reception and to process balloon APRS tracking transmissions but has many other applications including satellite operations and digital voice. The source code is in C, is available as open source 1 and runs on any UNIX-like operating system, including Mac OSX and Linux on Intel/ AMD x86 and ARM (e.g., Raspberry Pi) systems.
Standalone HAM Modulation Generator
By Anthony Le Cren, F4GOH
Abstract: I have always been interested in radio modulations like RTTY, PSK, WSPR, etc…. and especially to know how it’s coded. The asset of these modulations is understanding the DDS (Direct Digital Synthesis) operating principle. Then, you will be able to generate any modulation.
Study on Actual Usage of FT 8 in the US and Japan
By Masaaki Maeda, JR1AQN/W2
Abstract: This study is based on a demonstration of JT 65 / FT 8 at the 2017/2018 Hamvention, and an accompanying questionnaire given to FT 8 users. The purpose of the questionnaire was to find differences in usage by FT 8 users in the United States and Japan. The study revealed differences in usage frequency between Japan and the US, RF output on the Japan side being higher. We also found that users in both regions recognize a common appeal in FT 8 — that it allows quick and efficient QSO while reducing language barriers. We also found that many users are spending most of their QSO time on FT 8 and communicating with many DXCC entities. There is also great potential for FT 8 in petition mode.
Build and Configure your Space Weather Station with RF-Seismograph on a Raspberry Pi 3+
By Alex Schwarz, VE7DXW
Abstract: The MDSR and the RF-Seismograph are very stable and well established amateur radio software packages enabling users to extend the capability of their analog radios to SDR. The MDSR software provides a real time spectrum analyzer and IF DSP filtering with extremely clean RX audio and high dynamic range. The RF-Seismograph is a propagation scanner that monitors and records up to 6 different bands for long term propagation monitoring of 24h (6h are displayed). This software checks the NOAA Space Weather alert system every 10min for updates. It also includes a FTP upload service that allows the user to upload the measurement graphics to a web-server, for usage in websites to display real time propagation on the web. Individual propagation events are also listed in the Propagation Tracker. This creates an HTML page for additional on-line propagation updates.
Installing a LIF port into the TS-590 Transceiver
By Alex Schwarz, VE7DXW
Abstract: This document describes the procedure for installing an LIF (Low Intermediate Frequency [9 18kHz]) port in the TS-590 transceiver. This transceiver uses an interesting approach of IF filtering and pass-band tuning. It is a hybrid system that uses DSP filtering and crystal filters simultaneously. The IF bandwidth is changed by using IF band-pass tuning and two high quality IF filters. If the pass band settings go below filter one (10.695MHz ) the radio switches to an in-band 1st IF of 11.374MHz. This allows seamless adjustment of the analog filter bandwidth for CW mode up to 5kHz for AM.
Dynamic Range Tests of WSJT X and WSPR on 630m Using AGC with IC-7300
By Rob Sherwood, NCØB
Abstract: The dynamic range of the system, which consisted of an Icom IC-7300, a Monitor Sensors 160m to 630m transverter, and an HP Elite 8300 i7 computer, is approximately 75 dB when running AGC. Impulse noise capturing AGC may be more of a problem with shorter cycle times, such as with FT8’s 15 second cycle time, than with JT9’s 60 second or WSPR’s 120 cycle times.
Impulse noise capturing AGC is a design flaw in most radios with DSP that have shipped in the past 10 years, exclusive of the Elecraft K3 or K3S, late Apache SDR software, and some Ten-Tec products.
How to Kill Packet-Radio & APRS? Come to Serbia!
By Miroslav “Misko” Skoric, YT7MPB
Abstract: In this paper, we continue analyzing pervasive failures in Serbian policymakers’ strange decision, as well as continued country’s ham radio leadership’s wrongdoings – that all together significantly contributed not only to the stagnant status but also in the visible extinction of national-wide VHF & UHF ham radio data infrastructures.
